Fail-safe piston and cylinder arrangement



June 10, 1969 E. E. MUELLER 3,448,662

FAIL'SAFE PISTON AND CYLINDER ARRANGEMENT Filed Dec. 9, 1966 Sheet of 3I N VENTOR.

June 10, 1969 MUELLER I 3,448,662

FAIL-SAFE PISTON AND CYLINDER ARRANGEMENT Filed D80. 9, 1966 Sheet 2 GM.wm v E L M m 5 w 5 I I If 11171002 ,1! If r HTTOPNEYS I June 10, 1969 ME 3,448,662

FAIL'SAFE PISTON AND CYLINDER ARRANGEMENT Filed Dec. 9, 1966 7 Sheet of3 United States Patent 3,448,662 FAIL-SAFE PISTON AND CYLINDERARRANGEMENT Ernest E. Mueller, Kew Gardens, N.Y., assignor to OzoneMetal Products Corp., Ozone Park, N.Y., a corpora tion of New York FiledDec. 9, 1966, Ser. No. 600,636 Int. Cl. F15b 15/17, 11/08; F16b 13/04U.S. Cl. 91415 9 Claims ABSTRACT OF THE DISCLOSURE Background of theinvention There are known in the prior art piston and cylinderassemblies for lowering and raising heavy loads and for positioning thesupported member in a desired position. One application of such devicesis the support of a cargo aircraft ramp, the lowered position of whichis determined by the nature of the terrain on which the operation is tobe performed. Installations of this type usually employ a pair ofassemblies, the cylinder of each of which is carried by the aircraftbody and the piston of which is secured to the ramp. Fluid underpressure is supplied to the cylinders to lower and to raise the ramp asrequired.

It will readily be appreciated that, in an installation of the kinddescribed, a loss of operating pressure creates an extremely dangerouscondition since it results in the ramp falling substantially freely tothe ground. Attempts have been made in the prior art to overcome thisproblem by providing an assembly which fails safe. These systems may,for example, have an incremental mechanical lock to ensure that thesupported member, such as the ramp, will not fall freely in the eventthat pressure is lost. Fail-safe assemblies of the prior art arerelatively complicated and are consequently expensive. Moreover, theyare not all as certain in operation as is desirable. They incorporate anundesirable backlash and do not provide as stiff a system as may berequired.

In most installations of the prior art a mechanical device such as awinch is provided for moving the supported member in the event of apressure failure. Such a procedure in the prior art, however, isrelatively complicated and difiicult owing to the fact that no means isprovided for ensuring that the supported member will be moved to theposition it occupied under the action of the hydraulic system beforefailure.

Summary of the invention I have invented a fail-safe piston and cylinderarrangement which overcomes the defects of assemblies of the prior artpointed out hereinabove. My assembly is relatively simple inconstruction and operation. It is inexpensive to construct as comparedwith systems of the prior art. It is certain in operation. It has nobacklash and will lock in precisely the position of the supported memberupon failure of pressure. My assembly includes means for ensuring thatmechanical operation after failure will position the supported elementin precisely that position it occupied before fluid pressure failure.

One object of my invention is to provide a hydraulic piston and cylinderarrangement which fails safe.

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Another object of my invention is to provide a failsafe piston andcylinder arrangement which overcomes the defects of arrangements of theprior art.

A further object of my invention is to provide a failsafe piston andcylinder assembly which is simple in construction and certain inoperation.

Still another object of my invention is to provide a fail-safe pistonand cylinderarrangement which is relatively inexpensive as compared withsystems of the prior art.

Yet another object of my invention is to provide a fail-safe piston andcylinder arrangement which rernembers the position to which it had beenmoved by the hydraulic system before failure thereof.

Other and further objects of my invention will appear from the followingdescription.

In general my invention contemplates the provision of a hydraulic pistonand cylinder assembly in which fluid under pressure is applied to thehead side and through a one-way poppet valve to the rod side of theassembly for one direction of movement of the supported member. Formovement in the other direction I apply fluid under pressure to the rodside and connect the head side to the exhaust. I may provide my assemblywith an auxiliary slave piston which remains in the position to which ithas been moved by the main piston when the main piston is movedmechanically from that position after a failure.

Brief description of the drawings In the accompanying drawings whichform part of the instant specification and which are to be read inconjunction therewith and in which like reference numerals are used toindicate like parts in the various views:

FIGURE 1 is a fragmentary partially schematic view illustrating oneapplication of my fail-safe piston and cylinder arrangement.

FIGURE 2 is a sectional view of the installation of FIGURE 1 taken alongthe line 22 of FIGURE 1.

FIGURE 3 is a sectional view of one of my fail-safe piston and cylinderarrangements taken along the line 3-3 of FIGURE 1 and drawn on anenlarged scale.

FIGURE 4 is a sectional view of the fail-safe piston and cylinderarrangement shown in FIGURE 3 taken along the line 44 of FIGURE 3 anddrawn on an enlarged scale.

FIGURE 5 is a fragmentary sectional view of an alternate embodiment ofmy fail-safe piston and cylinder assembly.

Description of the preferred embodiments Referring now to FIGURES 1 and2, by way of example I have illustrated an installation wherein two ofmy assemblies, indicated generally by the reference characters 10 and12, are adapted to support a ramp 14 carried .by a hinge .16 on the body18 of an aircraft or the like. Each of the assemblies includes acylinder 20 and a piston rod 22, the lower end of which carries a clevis24 which receives a bracket tongue 26 to which it is pivotally securedby a bolt 28. Each assembly further includes a spherical bearing housing30. Bolts 32 or the like secure a mounting flange 34 on housing 30 to abracket 36 carried by the body 18.

I provide each of the assemblies 10 and 12 with a fitting 38 connectedby a line 40 to the head end inlet port fitting 42 of the assembly.Another fitting 44 leads to the rod end inlet port of the cylinder. Iprovided the system shown in FIGURE 1 with a control valve indicatedgenerally by the reference character 46 having a housing 48 whichslida'bly receives a spool 54 having a pair of lands 50 and 52. Anactuating rod 56 extending out of the housing 48 permits the spool 54 tobe posi- 3 tioned. A first outlet port 58 in the body 48 is connected bya line 60 to a common line 62 leading to both rod end inlet ports of theassemblies and 12. A second outlet port 64 in the body 48 is connectedby a line 66 to a common line 68 leading to both the head end inletports of the assemblies.

A line 70* connects a first inlet port 72 to a suitable source (notshown) of fluid under pressure through an on-otl valve 73. A line 74connects an exhaust port 76 in body 48 to the atmosphere or to a regionof reduced pressure.

In one position of the spool 54 illustrated in full lines of FIGURE 1,the inlet port 72 is connected to both outlet ports 58- and 64. In theother position of the spool 54, port 58 is connected to inlet port 72and .port 64 is connected to exhaust port 76. I have illustrated thisposition of the spool in broken lines in FIGURE 1.

Referring now to FIGURES 3 and 4, the cylinder slidably receives apiston 78 carried by the rod 22. Packing 80 provides a seal between thepiston and the cylinder wall. Additional packing 82 seals one end of thecylinder with the piston rod. The spherical bearing housing 30 receivesa bearing 84 carried by the cylinder 22 to permit limited tiltingmovement thereof of about 5. I close the end of the cylinder by means ofan end cap 86 screwed into the cylinder. Packing 88 seals this end ofthe cylinder.

My assembly includes an auxiliary piston 90 slidably supported on therod 22. Packing 92 and packing 94 respectively seal the auxiliary piston90 to the cylinder wall and to the rod 22. I form the rod 22 as a hollowrod and provide the clevis 24 with a bore 96 which communicates with thehollow interior of the rod. An opening 98 in the rod wall between theauxiliary piston 90 and the main piston 78 permits the passage of fluidfrom between the pistons into the hollow rod and out through passage 96for reasons which will be described hereinbelow. Line 40 is connected byfitting 42 to an inlet passage 100' leading to the head side of thecylinder.

The fitting 44 connects the line 62 to an inlet port 102 connected by apassage 104 to a valve assembly indicated generally by the referencecharacter 106. I arrange the various parts of the valve assembly 106 ina bore 108 adjacent the spherical bearing 84. The valve 106 includes aseat 110 formed with an opening 112 communicating with passage 104. Aspring 114 bearing between a retainer button 116 and a backup element118 normally urges a poppet 120 slidably supported in a bore 122 in thevalve housing 124 into engagement with the seat 110. A passage 126connects the opening 112 with the interior of the cylinder on the rodside of the piston when the poppet 120 moves away from seat 110 againstthe action of the spring 114.

A bore 128 extending into the bore 108 from outside the cylinder wallthreadably receives an actuating element 130 having a screwhead 132which permits the actuator to be turned to move the poppet 120 away fromseat 110 as will be described hereinafter. Preferably I provide the bore128' with a cap 134 which must be removed before the actuator is turned.

Referring now to FIGURE 5, as an alternative to the screw-type actuator130, I may provide an actuator 136 slidably received in a bore, such asthe bore 128, and extending outwardly therefrom. A lever 138 pivotallysupported on a pin 140 outside the bore can be turned slightly in acounterclockwise direction as viewed in FIG- URE 5 to push the actuatordown to move the poppet 120 away from the seat 110.

I may also provide my assembly with a thermal relief valve indicatedgenerally by the reference character 142. Valve 142 includes a seat 144disposed in a bore 146 leading into the cylinder. The valve element 148of the assembly 142 is urged by a spring 150 disposed in a block 152into engagement with the seat 144. When, owing to an increase intemperature the liquid expands, the element 148' is moved away from itsseat, it provides communication between the bore 146 and a bore 154leading into port 156.

In operation of my improved piston and cylinder arrangement in aninstallation such, for example, as that shown in FIGURE 1, when I desireto lower the ramp I move the spool 54 to a position at which the supplyline 70 is connected to both ports 58 and 64. I operate valve 73 tosupply fluid under pressure to connect the supply of fluid underpressure to line 70 thus to supply fluid under pressure both to the headside and to the rod side of the cylinder. The fluid supplied to line 68flows through lines 40 to the head side of both of the assemblies 10 and12. Fluid supplied to the line 62 moves the poppet 120 of each of theassemblies away from its associated seat to permit the fluid to flowinto the rod side of the cylinder. Owing to the fact that the pressureat the head side works on a greater area than does that at the rod side,the rod 22 of each of the assemblies is extended to lower the ramp. Whenthe ramp has been lowered to the desired position, the supply of fluidis cut off by operation of valve 73 and the ramp remains in thatposition.

When the ramp is to be raised, spool 54 is moved to the broken lineposition shown in FIGURE 1 to connect the line 70 to port 58 and toconnect port 64 to the exhaust line 74. Valve 73 is again opened and,under these conditions, fluid under pressure is supplied to the rod endof both assemblies and the head ends of the assemblies are connected toexhaust. The pressure acting on the rod sides of the pistons will raisethe ramp.

If at any time fluid pressure is lost, the back pressure on the rodsides of the assemblies moves both poppets 120 into engagement withtheir seats to trap fluid in the rod sides to hold the supported memberssuch as the ramp 14 in position.

It will be appreciated that as the ramp is being lowered, the auxiliaryor slave pistons of each of the assemblies move with the main pistons78. Should fluid pressure be lost and an auxiliary mechanical means suchas a winch (not shown) be used to raise the ramp from that position, theauxiliary pistons 90 will remain in the positions to which they weremoved as the ramp was lowered. Moreover, if after the ramp has beenraised by mechanical means it is desired to restore it to its formerlowered position, the main pistons 78 will move down until they engagethe auxiliary pistons 90 so that the ramp is returned precisely to thatposition it occupied before being raised.

An internal pressure lockup is relieved by operating either the actuator130 or the actuator 136 to move the poppet out of engagement with itsseat.

It will be seen that I have accomplished the objects of my invention. Ihave provided a hydraulic piston and cylinder arrangement which failssafe. My assembly overcomes the defects of fail-safe piston and cylinderassemblies of the prior art. It is simple in construction and certain inoperation. It is relatively inexpensive. My system incorporates meansfor ensuring that the supported member will be returned to the positionfrom which it was moved mechanically after a pressure failure.

Having thus described my invention, what I claim is:

1. A hydraulic piston and cylinder assembly including in combination, acylinder, a piston mounted for movement within said cylinder, a rodcarried by said piston, said cylinder having a rod end and a head end, asource of liquid under pressure, means connecting both the rod end andthe head end of said cylinder to said source to move said rod out ofsaid cylinder, said connecting means comprising a one-way poppet valvebetween the source and the rod end of the cylinder, a seat for saidvalve between said valve and said source, an auxiliary piston slidablycarried by said rod, and means forming an exhaust opening in said rodleading to the space between said pistons.

2. A piston and cylinder assembly for controllably raising and loweringa controlled member which normally moves downwardly under the influenceof gravity including in combination, a cylinder, a piston mounted formovement within said cylinder, a rod carried by said piston, saidcylinder having a rod end and a head end, means connecting said rod tosaid member for movement of the rod out of the cylinder to lower themember and for movement of the rod into the cylinder to raise themember, conduit means connecting both the rod end and the head end ofsaid cylinder to said source to move said rod out of said cylinder tolower said member,

said conduit means comprising a one-way poppet valve between the sou-roeand the rod end of the cylinder and a seat for said valve between saidvalve and said source, said valve moving into engagement with said seatupon failure of the pressure of said source to trap liquid in the rodend of said cylinder to prevent said member from moving downward freelyunder the influence of gravity, and manually operated means for openingsaid valve independently of fluid pressure in said conduit means.

3. A piston and cylinder assembly as in claim 2 in which said valve isnormally closed.

4. A piston and cylinder assembly as in claim 2 including a spring forbiasing said valve closed.

5. A piston and cylinder assembly as in claim 2 in which said valve isnormally closed and which said manually operated means includes a lever.

'6. A piston and cylinder assembly as in claim 2 including an auxiliarypiston adapted to move with said main piston in one direction ofmovement thereof.

7. A piston and cylinder assembly as in claim 2 including an auxiliarypiston slidably mounted on said rod.

8. A hydraulic piston and cylinder assembly as in claim 2 including anauxiliary piston slidably mounted on said rod, said first-named pistonbeing a main piston, said piston rod being hollow and open to theatmosphere at its end remote from said main piston, the rod wall beingformed with an opening between the main and auxiliary pistons.

9. A piston and cylinder assembly as in claim 2 including a thermalrelief valve in the wall of said cylinder on the rod side of saidpiston.

References Cited UNITED STATES PATENTS 2,517,406 8/1950 Mott 91-468 X2,764,131 9/ 1956 Knights 92-62 2,966,139 12/1960 Appel 91-415 X3,088,283 5/1963 Furia et al. 91447 X 3,174,410 3/1965 Booth et a1. 91-419 3,273,468 9/1966 Allen 91-436 CARROLL B. DORITY JR., PrimaryExaminer.

US. Cl. X.R.

